Cousins are like stair steps.
Grandparents are on the platform above the first generation or first step.
First Gen: Their 4 children (My dad and his siblings)
Second Gen: Their 8 children (Me, my siblings, my (first) cousins are dad's nieces and nephews (children of dad's sisters and brothers.
Third Gen: Our 16 children (My children are dad's grandchildren. My cousins once removed are dad's grand nieces and nephews (grandchildren of dad's sisters and brothers)
Fourth Gen: My grandchildren and dad's great-grand children. Dad's great-grand nieces and nephews are my second cousins. These are the children born to 1C1R (first cousin once removed)
Cousins can be complicated.
My parents had no siblings. Their parents had a 14 siblings and cousins by the dozens. I did not know what a cousin was. I was in my 60s before I met a first cousin. She is the grandchild of my maternal grandfather's brother. Both lines daughtered out. It took me a very long time to understand the 1C1R concept primarily due to corrupted records found on the Internet.
I had one person claim a direct relationship to me because her great-grandmother's, half-sister's son, married my grandmother's aunt. She also claimed the same to the other member of the family based on another of the great-grandmother's half-sisters who married a great-grandfather. There was hitch in her get-along that day. They had no children. It continued to a third claim based on my grandfather's sister who married her grandmother's brother's daughter. Their children never married or had issue.
All you need is a 1 large family, and 1 common name for these people to find you.